(1) Field of the Invention
This invention relates to a high-frequency motor incorporating a tool drawing-up device therein.
(2) Description of the Prior Art
In the machine tool, a high-frequency motor is used as a main shaft, then a tool is inserted in a rotary shaft of the high-frequency motor. The tool is drawn to be secured to the tip end of the rotary shaft by means of a tool drawing-up device. However, this depends upon the drawing-up force of the spring in the past, so that when the stronger load than the spring force is applied to the tool, it is slipped to cause the so-called fretting phenomenon.
This phenomenon may be prevented if the powerful spring is mounted in the high-frequency motor, however the result has defects that the high-frequency motor becomes large-sized and expensive construction.